This invention generally relates to wrench tools and pertains more particularly to wrenches of the type which employ a flexible strap-like element to grip the object which is to be manipulated.
Pipe wrenches and jar openers having a flexible, strap-like element adapted to be wrapped around the object to be gripped are generally known in the art. A torque applying lever element is typically connected to the strap in some manner and contacts the surface of the object at a relatively restricted zone, which serves as a fulcrum about which a force applied by the user is transmitted partially to the strap in order to twist or turn the object in a wrenching manner, but partially as an inwardly directed and substantial force of engagement of the lever with such fulcrum zone of the workpiece.
Known prior art broadly related to the same field as the present invention is disclosed in U.S. Pat. Nos. 785,711; 1,051,562; 1,667,620; and 2,422,715. Such prior art patents disclose tools which are either unnecessarily complex or less than completely effective in terms of the efficiency with which the force that is manually applied by the user is effectively translated to a torque for wrenching the object being gripped. Moreover, the more analagous prior art wrenches may not be used in conjunction with rather delicate workpieces such as thin-walled chrome-plated pipes and plastic pipes, since the prior art designs place concentrated, inwardly directed stresses on the workpiece which can damage the surface, or even crush wall portions, of the workpiece. Thus, a need exists for a practical and effective wrench device which may be conveniently and safely used with the rather delicate variety of pipes now in widespread use, and which avoids structural damage to such pipes while at the same time providing the comparatively high magnitudes of torque necessary for manipulation of such pipes in their usual applications such as plumbing fixturing.
The present invention overcomes the deficiencies inherent in prior art wrench designs, by providing a tool which is simple in construction and easily used, yet which is particularly effective in translating the manually applied force to a torque on the workpiece, while also distributing the stresses over the surface area of the workpiece in a manner to avoid damage to the more delicate types of workpieces. According to one embodiment of the present invention, an elongate, resilient, spiralled strip has the outer end thereof connected to an elongate force applying handle. The free inner end of the strip has a friction pad secured thereto for initially gripping the surface of the workpiece when the user slips the strip around the workpiece and twists the handle in a wrenching manner. The handle includes an arcuate, concave surface portion adjacent the outer end of the strip, which is adapted to complementally engage a substantial surface portion of a generally cylindrical workpiece. The arcuate portion of the handle functions to apply a turning force to the outer end of the strip upon turning of the handle in a manner to translate most of the turning force to a tension force on the strip, rather than into an inwardly directed force upon the workpiece, while also functioning to distribute the inwardly directed components of the applied turning force over a wider area of the workpiece surface in order to avoid stress concentrations on the workpiece, and possible resultant damage thereto. An alternate embodiment of the invention further provides a housing compartment integral within the handle for storing a length of the strip, a selected portion of which may be removed from the handle in order to accommodate workpieces having different circumferences.
A primary object of the invention is to provide a strap tool for gripping and turning delicate, generally cylindrically-shaped workpieces, which is effective in applying a relatively large magnitude of torque to the workpiece, but yet which avoids marring, denting, crushing or otherwise damaging the workpiece.
Another object of the invention is to provide a wrench which includes a strap element adapted to be wrapped around the workpiece for gripping and turning the latter, wherein an increased amount of the force applied to the wrench by the user is translated into a turning, tension force on the strap in a direction tangent to the surface of the workpiece, rather than into a potentially damaging and wasted force directed inwardly toward the longitudinal axis of the workpiece.
A further object of the invention is to provide a wrench of the mentioned type which obviates the need for tensioning adjustment means or mechanism for retaining the strap element in securement around the workpiece. As a corollary to the foregoing object it is a still further object to provide a wrench having a gripping strap element which is particularly simple in construction and which may be quickly and easily secured in operative relationship to the workpiece.
Another object of the invention is to provide a wrench having a gripping strap element which may be selectively adjusted in length to accommodate workpieces of various sizes.
Other and further objects of the invention will be made clear or become apparent in the course of the following description of a preferred and alternate embodiment of the invention.